The present invention relates in general to a lead path configuration for an electric device and, more particularly, to an improved lead path configuration for a generator rotor used in a power generation plant.
Many power generation plants produce electricity by converting energy (e.g. fossil fuel, nuclear fission, hydraulic head and geothermal heat) into mechanical energy (e.g. rotation of a turbine shaft), and then converting the mechanical energy into electrical energy (e.g. by the principles of electromagnetic induction).
Some of these power generation plants, such as a fossil-fuel power generation plant, comprise a turbine, a generator and an exciter. The turbine, generator and exciter are typically coupled to each other in axial alignment, with the generator located between the turbine and the exciter.
The turbine converts fossil fuel energy into mechanical energy in the form of turbine shaft rotation through a steam or combustion cycle. The generator then converts the rotational energy into electrical energy. The generator includes an axially extending rotor journaled in an annular stator that surrounds and sleeves the rotor. The rotor has a shaft in which conductive coil windings are axially arranged. The stator has punchings that collectively from an annular core in which conductive coil windings are positioned parallel with respect to the axial rotor coils. As the turbine shaft rotates the generator rotor, the exciter provides an electrical current to the rotor coil windings. The rotating electrically charged rotor creates a magnetic flux that induces an electrical current in the stationary stator coil windings. This induced electrical current is then drawn from the stator and constitutes the electricity that the power generation plant provides to electricity consumers.
One aspect of the above-described power generation scheme involves the electrical interconnection of the exciter and generator. An electrically conductive lead path is used to transport current in a closed loop configuration from the exciter, through the generator rotor coil windings, and then back to the exciter. It has been observed that, as a result of prolonged generator use, the lead path can physically sever or otherwise fail to properly carry current. Among other things, lead path failure can cause electric arcing or re-routing of the electric current through nearby conductive materials. Arcing and re-routing can, among other things, melt portions of the generator shaft and otherwise damage the generator.
It has also been observed that some portions of the lead path tend to fail more often than other portions of the lead path. In particular, it has been observed that lead path failure tends to occur along a portion of the lead path around area A shown in FIG. 2.
There is thus a need for a lead path that inhibits, if not prevents, lead path failure. There is also a need for a portion of a lead path that is particularly suited to inhibit, if not prevent, lead path failure path around area A shown in FIG. 2. There is further need for a lead path that improves upon the prior art.
The present invention provides a lead path that inhibits, if not prevents, lead path failure, especially around area A shown in FIG. 2. The present invention also provides a method of assembling or fitting the lead path of the present invention into a generator. The present invention further provides a method of repairing or retrofitting a lead path that has failed or is susceptible to failure with the lead path of the present invention. The present invention also recognizes that causes of lead path failure around area A shown in FIG. 2 are relatively unknown. Thus, the present invention also provides assistance in determining causes of lead path failure and identifies ways to overcome lead path failure.
One aspect of the present invention thus involves an apparatus adapted to form a conductive path for carrying an electric current in a generator. The apparatus comprises an electrically conductive axial lead having a first end and a second end, and forming a portion of the conductive path. The apparatus further comprises an electrically conductive strap having a first end and a second end, and forming a portion of the conductive path. The apparatus further comprises an electrically conductive radial lead having a first end and a second end, the radial lead forming a portion of the conductive path and coupled to the axial lead and to the strap, the radial lead not being supported by a blower hub wedge portion of the generator.
Another aspect of the present invention thus involves a method of retrofitting an electrical lead path of a generator. The method comprises removing at least a portion of an electrically conductive radial lead from the generator, the radial lead including a radially extending arm. The method further comprises removing at least a portion of an electrically conductive strap from the generator, the strap including a first end and a second end and adapted to attach to the radial lead. The method further comprises inserting at least one electrically conductive component into the generator to form at least a portion of the lead path, the at least one electrically conductive component including a modified radial lead having a radially extending portion. The method further comprises coupling the modified radial lead to the conductive strap. Whereby, the location of the radially extending portion of the modified radial lead within the lead path is inboard of the location of the radially extending arm of the removed radial lead within the lead path.
Yet another aspect of the present invention thus involves a method of choosing a plurality of electrically conductive components to inhibit electrical failure in a lead path of a generator. The method comprises identifying at least one phenomenon that may cause lead path failure. The method further comprises providing a plurality of electrically conductive components adapted to inhibit the identified at least one phenomenon from causing lead path failure, the plurality of electrically conductive components including a component constructed of a high strength conductive material capable of withstanding the stress and load forces produced by the generator during normal generator operation. The method further comprises arranging and attaching the plurality of electrically conductive components to form the lead path.
Further aspects, features and advantages of the present invention will become apparent from the drawings and detailed description of the preferred embodiment that follows.